A laptop computer, also known as a notebook computer, is a small personal computer designed for mobile use. A laptop integrates all of the typical components of a desktop computer, including a display, a keyboard, a pointing device (a touchpad, also known as a trackpad, or a pointing stick) and a battery into a single portable unit. The rechargeable battery is charged from an AC/DC adapter and has enough capacity to power the laptop for several hours, enabling it to be used virtually anywhere.
A laptop is usually shaped like a large notebook with thickness of 0.7-1.5 inches (1.7-4cm) and dimensions ranging from 10x8 inches (27x22cm, 13" display) to 15x11 inches (39x28cm, 17" display) and up. Modern laptops weigh , and some older laptops were even heavier. Most laptops are designed in the flip form factor to protect the screen and the keyboard when closed.
Originally aimed at professionals "on the go", early laptops were expensive, limited in capabilities and heavy. They were relatively incommon, with desktops occupying most of the personal computer market: in 1996, just 17% of personal computers sold worldwide were laptops . However, as the advance of technology made notebook computers more capable, as prices fell from several thousand dollars to several hundreds for basic models, and as more and more people found themselves using computers daily, the compactness and the portability of laptops made them the personal computers of choice for many consumers. It is now expected that more laptops than desktops will be sold as soon as 2009.
Laptops began from a desire to have a full-featured computer that could be easily used anywhere. These all-in-one systems could be easily transported, but were heavy and usually were not battery powered. The cathode ray tube (CRT) was one of the major reasons portable computers were so large and heavy, but the use of a full-size desktop motherboard with room for ISA expansion cards was another size factor.
It was the transition to LCD and plasma displays that permitted the luggable to shrink in size and become the first real laptop, though at first still without internal batteries. Battery technology improvements and the introduction of smaller devices such as the 3.5-inch floppy disk permitted a gradually more compact and sophisticated complete portable system.
A replacement computer is a personal computer that provides the full capabilities of a desktop computer while remaining portable. They are often a larger, bulkier laptop. Because of their increased size, this class of computer usually includes more powerful components and a larger display than generally used in smaller portable computers and can have a relatively limited battery capacity (or none at all). Some use a limited range of desktop components to provide better performance per dollar at the expense of battery life. These are sometimes called desknotes, a portmanteau of the words "desktop" and "notebook," though the term is also applied to desktop replacement computers in general.
Powerful laptops are meant to be mainly used for fun and infrequently carried out due to their weight and size; the latter provides more space for powerful components and a big screen, usually measuring 17–20 inches (43–51 cm). Desktop replacements tend to have limited battery life, rarely exceeding three hours, because the hardware is not optimized for efficient power usage. Sometimes called a luggable laptop. An example of a desktop replacement computers are gaming notebooks, which are designed to handle 3D graphic-intensive processing for gamers.
Laptops weighing typically between 0.8 to 2.7 kg and a screen of 6.4 to 13.3 inches diagonally. A subnotebook is a small and lightweight portable computer, with most of the features of a standard laptop computer but smaller. The term is often applied to systems that run full versions of desktop operating systems such as Windows or Linux, rather than specialized software such as Windows CE, Palm OS or Internet Tablet OS.
Subnotebooks are smaller than laptops but larger than handheld computers and UMPCs. They often have screens around 10.6" (26.92 cm) (diagonal) and weigh less than 1 to 2 kg, as opposed to full-size laptops with 14.1" (35.81 cm) or 15.4" (39.12 cm) screens that typically weigh 2 kg or more. The savings in size and weight are usually achieved partly by omitting ports or having removable media/optical drives; subnotebooks are often paired with docking stations to compensate.
Laptops contain components that are similar to their desktop counterparts and perform the same functions, but are miniaturized and optimized for mobile use and efficient power consumption, although typically less powerful for the same price. Most laptops use different memory modules for their random access memory (RAM), for instance, SO-DIMM in lieu of the larger DIMMs. An external keyboard or mouse can usually be attached.
Most modern laptops feature 12 inch (30 cm) or larger active matrix displays with resolutions of 1024×768 pixels and above, and have a PC Card (formerly PCMCIA) or ExpressCard expansion bay for expansion cards, one or more USB ports, and a external monitor port (VGA or DVI). Most laptops have also an ethernet network port. Some have legacy ports such as a PS/2 keyboard/mouse port or a serial port, parallel port, and S-video or composite video port. Hard disks are physically smaller—2.5 inch (60 mm)—compared to the standard desktop 3.5 inch (90 mm) drive, and usually have lower performance and power consumption. Video and sound chips are usually integrated. This tends to limit the use of laptops for gaming and entertainment, two fields which have constantly escalating hardware demands, however, higher end laptops can come with dedicated graphics processors. These mobile graphics processors tend to have less performance than their desktop counterparts, but this is because they have been optimized for lower power usage. Some subsystems, such as Wi-Fi, come in contemporary laptops on replaceable MiniPCI cards, usually accessible through a door on the bottom. Memory modules (smaller than the usual DIMMs) are often also accessible through the bottom, though some may be on the motherboard under the keyboard and thus not meant to be accessed by the user.
There is a wide range of laptop specific processors available from Intel (Pentium M, Celeron, Intel Core and Intel Core 2), AMD (Athlon, Turion 64, and Sempron) and from VIA (C3 and C7-M). Motorola and IBM developed and manufactured the chips for the former PowerPC-based Apple laptops (iBook and PowerBook). Generally, laptop processors are less powerful than their desktop counterparts, due to the need to save energy and reduce heat dissipation.
Current models of laptops utilize lithium ion batteries with more recent models using the new lithium polymer technology. These technologies have largely replaced the older nickel metal-hydride batteries. Typical battery life for most laptops is two to five hours with light-duty use, but may drop to as little as one hour with intensive use. Batteries gradually deteriorate over time and eventually need to be replaced in one to five years, depending on the charging and discharging pattern.
This very powerful main battery should not be confused with the much smaller battery nearly all computers use to run the real-time clock and backup BIOS configuration into the CMOS memory when the computer is without power.
Virtually all laptops can be powered from an external AC converter. This device typically adds half a kilogram (1 lb) to the overall "transport weight" of the equipment.
Docking stations became another common laptop accessories in the early 1990s. They typically were quite large and offered 3.5" and 5.25" storage bays, one to three expansion slots (typically AT style), and a host of connectors. The mating between the laptop and docking station was typically through a large, high-speed, proprietary connector. The most common use was in a corporate computing environment where the company had standardized on a common network card and this same card was placed into the docking station. These stations were very large and quite expensive. As the need to additional storage and expansion slots became less critical because of the high integration inside the laptop itself, the emergence of the Port Replicator as a major accessory commenced. The Port Replicator was often a passive device that simply mated to the connectors on the back of the notebook and allowed the user to quickly connect his laptop so VGA, PS/2, RS-232, etc. devices were instantly attached. As higher speed ports like USB and Firewire became commonplace, the Port Replication was accomplished by a small cable connected to one of the USB 2.0 or FireWire ports on the notebooks. Wireless Port Replicators followed.
A pointing stick or touchpad is used to control the position of the cursor on the screen. The pointing stick is usually a rubber dot that is located between the G, H and B keys on the laptop keyboard. To navigate the cursor, pressure is applied in the direction intended to move. The touchpad is touch-sensitive and the cursor can be navigated by moving the finger on the pad.
The main advantage of laptops over their larger desktop counterparts is the inherent portability. Another advantage is the laptop's ability to operate on battery power in the case of a power outage and less energy consumption.
Some hard drives and memory are commodity items and are interchangeable. However, other parts such as motherboards, keyboards, and batteries are proprietary in design and are only interchangeable within a manufactures brand and/or model line.
A significant point to note is that the vast majority of laptops on the market are manufactured by a small handful of Original Design Manufacturers (ODM). The ODM matters more than the Original Equipment Manufacturer (OEM). Major relationships include:
Due to their portability and tight integration, laptops are more subject to wear and physical damage than desktops. Components such as batteries, screen hinges, power jacks, and power cords are commonly subject to deterioration due to ordinary use. These components are usually expensive to replace, with a typical laptop battery costing US$130, the AC Adapter US$75.
Other parts are inexpensive, such as a power jack costing perhaps US$20, but replacement may require extensive disassembly and reassembly of layers of internal components. Other inexpensive but fragile parts often cannot be purchased separate from larger more expensive components. For example, the video display cable and backlight power cable that passes through the lid hinges to operate the screen will eventually break from opening and closing the lid hundreds of times over many years, and usually these tiny cables cannot be purchased separate from an entire US$400 LCD panel.
A liquid spill onto the keyboard, which is rather a minor mishap with a desktop system can damage costly components such as the motherboard or LCD panel. Dropping a laptop can damage the LCD screen if not break apart its body. The repair costs of a failed motherboard or LCD panel may exceed the purchase value of the laptop.
Laptops must also rely on extremely compact cooling systems involving a fan and heat sink that eventually fails due to filling with airborne dust and debris. Most laptops do not have any sort of removable dust collection filter over the air intake for these cooling systems, resulting in a system that gradually runs hotter and louder as the years pass. Eventually the laptop cooling is so choked with dust that it starts to overheat just from minor operational load. This dust is usually deeply buried inside where casual cleaning and vacuuming cannot remove it, and instead complete disassembly is needed to clean the laptop.
Additionally, the bodies of these laptops are typically made of a stiffer magnesium alloy instead of plastic, since it is the flexing of the circuit boards and fragile mechanical devices that causes the most damage. Hard drives are often mounted in soft shock-absorbing silicone mounts to greatly increase their chances of surviving a waist-high fall.
When a laptop hits the floor, the free-floating hard drive heads can slap against the spinning platter, scratching it and cause an irrepairable head crash that renders the hard drive unusable. Recently hard drives have been constructed which can move the read heads completely off the spinning platters, known as unloading. With the use of an accelerometer, the hardware can detect the sudden fall and park the heads off-platter before the laptop hits the ground. (See Sudden Motion Sensor.)
Many laptops have removable CPUs, although support for other CPUs is restricted to the specific models supported by the laptop motherboard. The socketed CPUs are perhaps for the manufacturer's convenience, rather than the end-user, as few manufacturers try new CPUs in last year's laptop model with an eye toward selling upgrades rather than new laptops. In many other laptops, the CPU is soldered and non-replaceable.
Many laptops also include an internal MiniPCI slot, often occupied by a Wi-Fi or Bluetooth card, but as with the CPU, the internal slot is often restricted in the range of cards that can be installed. The widespread adoption of USB mitigates I/O connectivity to a great degree, although the user must carry the USB peripheral as a separate item.
In February 2007, a new standard for external PCI Express cables and connectors was announced. Future laptops can be expanded using external PCI Express backplane and chassis.
For a given price range (and manufacturing base), laptop computational power has traditionally trailed that of desktops. This is partly due to most laptops sharing RAM between the program memory and the graphics adapter. By virtue of their usage goals, laptops prioritize energy efficiency and compactness over absolute performance. Desktop computers and their modular components are built to fit much bigger standard enclosures, along with the expectation of AC line power. As such, energy efficiency and portability for desktops are secondary design goals compared to absolute performance.
For typical home (personal use) applications, where the computer spends the majority of its time sitting idle for the next user input, laptops of the thin-client type or larger are generally fast enough to achieve the required performance. 3D gaming, multimedia (video) encoding and playback, and analysis-packages (database, math, engineering, financial, etc.) are areas where desktops still offer the casual user a compelling advantage.
As computer hardware miniaturization develops, laptops are beginning to close the performance gap with desktops. Intel's Core 2 line of processors is efficient enough to be used in portable computers, and many manufacturers such as Apple Inc., Lenovo and Dell are building Core 2 based laptops. Also, many high end laptop computers feature mobility versions of graphics cards, eliminating the performance losses associated with integrated graphics, while maintaining long battery life.
A study by State University of New York researchers says heat generated from laptops can significantly elevate the temperature of the scrotum, potentially putting sperm count at risk. The small study, which included little more than two dozen men ages 13 to 35, found that the sitting position required to balance a laptop can raise scrotum temperature by as much as 2.1 °C (3.8 °F). Heat from the laptop itself can raise the temperature by another 0.7 °C (1.4 °F), bringing the potential total increase to 2.8 °C (5.2 °F). However, further research is needed to determine whether this directly affects sterility in men. A common practical solution to this problem is to place the laptop on a table or desk.
Heat from using laptop on lap can also cause skin discoloration on the thighs.
Because of their small keyboard and trackpad pointing devices, the use of laptops can cause RSI, and for this reason laptops have docks that are used with ergonomic keyboards to prevent injury. The integrated screen often causes users to hunch over for a better view, which can cause neck or spinal injuries. Some health standards require that ergonomic keyboards be used in workplaces.
Boundaries that separate these categories are blurry at times. For example, the OQO UPC is a PDA-sized tablet PC; the Apple eMate had the clamshell form factor of a laptop, but ran PDA software. The HP Omnibook line of laptops included some devices small enough to be called handheld computers. The hardware of the Nokia 770 internet tablet is essentially the same as that of a PDA such as the Zaurus 6000; the only reason it's not called a PDA is that it doesn't have PIM software. On the other hand, both the 770 and the Zaurus can run some desktop Linux software, usually with modifications.
Laptops for children